Many different types of centrifugal separators are known for separating heterogeneous mixtures into components based on specific gravity. Typically, a heterogeneous mixture, which may also be referred to as feed material or liquid, is injected into a rotating bowl of a centrifugal separator. The rotating bowl spins at high speeds and forces components of the mixture that have a high specific gravity to separate therefrom by sedimentation. As a result, dense solids compress as a cake tightly against an inner surface or wall of the bowl and clarified liquid, or centrate, forms radially inward from the cake. The bowl may spin at speeds sufficient to produce forces 20,000 times greater than gravity so as to separate the solids from the centrate. As solids accumulate along the wall of the bowl, the centrate exits from the bowl and leaves the separator. Once a desired amount of solids has accumulated, the separator is placed in a discharge mode in which the solids are removed from the separator. Often, for example, an internal scraper is engaged to scrape the solids from the walls of the bowl.
Conventional separators have many shortcomings when discharging particular kinds of solids and liquids. For example, some separators may not be capable of completely discharging solids that are sticky, which can result in poor yields. A poor yield can be especially problematic for high-value solids such as those encountered in pharmaceutical processes. Traditional separators also subject a feed material to very high shear forces when accelerating the material to the rotational speed of the bowl, which can damage, for example, sensitive chemical or biological substances such as intact cells. Other separators do not provide a convenient means by which to handle and recover sensitive solids. For example, an operator is commonly required to assist with solids discharge and recovery, introducing the potential for contamination. Furthermore, conventional separators tend to be difficult to clean or sterilize in place, requiring operations that significantly increase maintenance costs and creating the potential for cross contamination between different preparations.
The biotechnology and pharmaceutical industries have come to rely increasingly on disposable process components for production. Disposable, pre-sterilized sample contacting materials offer numerous advantages, including savings in time, labor, and cost for both initial set-up and turn-around between runs. They also dramatically reduce the risk of contamination and simplify process validation. Conventional production scale centrifugal separators suitable for processing cells and other biomaterials require particular care to clean and sterilize in place. Nevertheless, to our knowledge no available separator offers the advantages of fully pre-sterilizable and disposable sample contacting elements.